The environment has long been known to play a big role in human health — from waterborne diseases like cholera to allergies caused by ragweed pollen. Now some researchers are blaming human-induced climate warming for killer European heat waves and even for increased incidence of malaria.
In response, many experts argue that public-health systems must prepare for new challenges. Planetary warming may stress already overburdened public-health systems, especially in developing countries.
In some cities, air quality is particularly susceptible to warming, as evidenced by that fact that summer ozone pollution and stagnant air masses make it harder for people with asthma or cardiovascular disease to breathe, according to Harvard Medical School's Center for Health and the Global Environment. The more severe drought and flood conditions predicted by some climate scientists could also mean widespread death and injury from worsened malnutrition, floods and landslides.
The range and severity of infectious diseases also may shift as climate alters.
The Harvard researchers say the range of malaria, one of the most disabling and widespread infectious diseases, already may be shifting and expanding due to climate change. Before the 1970s, for example, malaria did not afflict Africa's highlands. With warming, however, mountain glaciers have melted, and malaria-carrying mosquitoes have expanded their range into the mountains.
Conservative analysts, however, dispute the idea that malaria has only recently spread to non-tropical regions. Global-warming enthusiasts “made this up,” says Myron Ebell, director of global warming and international environmental policy at the big-business-funded Competitive Enterprise Institute. “Even in the Little Ice Age, we had malaria and dengue fever [another mosquito-borne disease] in Washington, D.C., and Oslo [Norway].”
But that criticism misses the point, according to Jonathan Patz, an associate professor of environmental studies and population health at the University of Wisconsin-Madison. The malaria parasite does show up in temperate regions, Patz says, but it's not a problem because the disease's ability to spread is restricted in moderate climates.
Patz says the danger comes if malaria spreads into a region that has become warmer, which some scientists say may be already happening in Africa. In warm climates, malarial parasites can thrive, and the disease spreads easily, becoming difficult for medicine to halt.
“You can't just do one thing and make it go away,” Patz says, so the spread into additional, warming regions would be a serious health threat.
“The lesson for the future is that we need to take a multi-pronged approach to the health effects of climate change,” he continues. “Number one, we need a strong public-health infrastructure. There also must be an awareness that these long-time environmental pressures can make disease prevention even harder.”
For example, if extreme weather events occur more often, as most climate-change models predict, floods that may have contaminated public water systems every 20 or 30 years in the past may become much more frequent. Then “there's a need to build that into public-health planning,” says Patz. “This is where environmental policy becomes the same as public-health policy.”
Putting environmental considerations back into the forefront of public health is in some ways a return to the past, Patz says. Before antibiotics and pesticides, “we used to be very environmentally oriented”” in medicine, concerned with sanitation and the spread of disease. “Medical schools used to have strong departments of vector ecology” — the study of organisms like mosquitoes that don't cause disease but carry disease-causing pathogens — “but these were dismantled.”
That focus needs to come back, Patz says.